1/***************************************************************************/
2/* */
3/* afhints.h */
4/* */
5/* Auto-fitter hinting routines (specification). */
6/* */
7/* Copyright 2003-2018 by */
8/* David Turner, Robert Wilhelm, and Werner Lemberg. */
9/* */
10/* This file is part of the FreeType project, and may only be used, */
11/* modified, and distributed under the terms of the FreeType project */
12/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
13/* this file you indicate that you have read the license and */
14/* understand and accept it fully. */
15/* */
16/***************************************************************************/
17
18
19#ifndef AFHINTS_H_
20#define AFHINTS_H_
21
22#include "aftypes.h"
23
24#define xxAF_SORT_SEGMENTS
25
26FT_BEGIN_HEADER
27
28 /*
29 * The definition of outline glyph hints. These are shared by all
30 * writing system analysis routines (until now).
31 */
32
33 typedef enum AF_Dimension_
34 {
35 AF_DIMENSION_HORZ = 0, /* x coordinates, */
36 /* i.e., vertical segments & edges */
37 AF_DIMENSION_VERT = 1, /* y coordinates, */
38 /* i.e., horizontal segments & edges */
39
40 AF_DIMENSION_MAX /* do not remove */
41
42 } AF_Dimension;
43
44
45 /* hint directions -- the values are computed so that two vectors are */
46 /* in opposite directions iff `dir1 + dir2 == 0' */
47 typedef enum AF_Direction_
48 {
49 AF_DIR_NONE = 4,
50 AF_DIR_RIGHT = 1,
51 AF_DIR_LEFT = -1,
52 AF_DIR_UP = 2,
53 AF_DIR_DOWN = -2
54
55 } AF_Direction;
56
57
58 /*
59 * The following explanations are mostly taken from the article
60 *
61 * Real-Time Grid Fitting of Typographic Outlines
62 *
63 * by David Turner and Werner Lemberg
64 *
65 * https://www.tug.org/TUGboat/Articles/tb24-3/lemberg.pdf
66 *
67 * with appropriate updates.
68 *
69 *
70 * Segments
71 *
72 * `af_{cjk,latin,...}_hints_compute_segments' are the functions to
73 * find segments in an outline.
74 *
75 * A segment is a series of at least two consecutive points that are
76 * approximately aligned along a coordinate axis. The analysis to do
77 * so is specific to a writing system.
78 *
79 *
80 * Edges
81 *
82 * `af_{cjk,latin,...}_hints_compute_edges' are the functions to find
83 * edges.
84 *
85 * As soon as segments are defined, the auto-hinter groups them into
86 * edges. An edge corresponds to a single position on the main
87 * dimension that collects one or more segments (allowing for a small
88 * threshold).
89 *
90 * As an example, the `latin' writing system first tries to grid-fit
91 * edges, then to align segments on the edges unless it detects that
92 * they form a serif.
93 *
94 *
95 * A H
96 * | |
97 * | |
98 * | |
99 * | |
100 * C | | F
101 * +------<-----+ +-----<------+
102 * | B G |
103 * | |
104 * | |
105 * +--------------->------------------+
106 * D E
107 *
108 *
109 * Stems
110 *
111 * Stems are detected by `af_{cjk,latin,...}_hint_edges'.
112 *
113 * Segments need to be `linked' to other ones in order to detect stems.
114 * A stem is made of two segments that face each other in opposite
115 * directions and that are sufficiently close to each other. Using
116 * vocabulary from the TrueType specification, stem segments form a
117 * `black distance'.
118 *
119 * In the above ASCII drawing, the horizontal segments are BC, DE, and
120 * FG; the vertical segments are AB, CD, EF, and GH.
121 *
122 * Each segment has at most one `best' candidate to form a black
123 * distance, or no candidate at all. Notice that two distinct segments
124 * can have the same candidate, which frequently means a serif.
125 *
126 * A stem is recognized by the following condition:
127 *
128 * best segment_1 = segment_2 && best segment_2 = segment_1
129 *
130 * The best candidate is stored in field `link' in structure
131 * `AF_Segment'.
132 *
133 * In the above ASCII drawing, the best candidate for both AB and CD is
134 * GH, while the best candidate for GH is AB. Similarly, the best
135 * candidate for EF and GH is AB, while the best candidate for AB is
136 * GH.
137 *
138 * The detection and handling of stems is dependent on the writing
139 * system.
140 *
141 *
142 * Serifs
143 *
144 * Serifs are detected by `af_{cjk,latin,...}_hint_edges'.
145 *
146 * In comparison to a stem, a serif (as handled by the auto-hinter
147 * module that takes care of the `latin' writing system) has
148 *
149 * best segment_1 = segment_2 && best segment_2 != segment_1
150 *
151 * where segment_1 corresponds to the serif segment (CD and EF in the
152 * above ASCII drawing).
153 *
154 * The best candidate is stored in field `serif' in structure
155 * `AF_Segment' (and `link' is set to NULL).
156 *
157 *
158 * Touched points
159 *
160 * A point is called `touched' if it has been processed somehow by the
161 * auto-hinter. It basically means that it shouldn't be moved again
162 * (or moved only under certain constraints to preserve the already
163 * applied processing).
164 *
165 *
166 * Flat and round segments
167 *
168 * Segments are `round' or `flat', depending on the series of points
169 * that define them. A segment is round if the next and previous point
170 * of an extremum (which can be either a single point or sequence of
171 * points) are both conic or cubic control points. Otherwise, a
172 * segment with an extremum is flat.
173 *
174 *
175 * Strong Points
176 *
177 * Experience has shown that points not part of an edge need to be
178 * interpolated linearly between their two closest edges, even if these
179 * are not part of the contour of those particular points. Typical
180 * candidates for this are
181 *
182 * - angle points (i.e., points where the `in' and `out' direction
183 * differ greatly)
184 *
185 * - inflection points (i.e., where the `in' and `out' angles are the
186 * same, but the curvature changes sign) [currently, such points
187 * aren't handled specially in the auto-hinter]
188 *
189 * `af_glyph_hints_align_strong_points' is the function that takes
190 * care of such situations; it is equivalent to the TrueType `IP'
191 * hinting instruction.
192 *
193 *
194 * Weak Points
195 *
196 * Other points in the outline must be interpolated using the
197 * coordinates of their previous and next unfitted contour neighbours.
198 * These are called `weak points' and are touched by the function
199 * `af_glyph_hints_align_weak_points', equivalent to the TrueType `IUP'
200 * hinting instruction. Typical candidates are control points and
201 * points on the contour without a major direction.
202 *
203 * The major effect is to reduce possible distortion caused by
204 * alignment of edges and strong points, thus weak points are processed
205 * after strong points.
206 */
207
208
209 /* point hint flags */
210#define AF_FLAG_NONE 0
211
212 /* point type flags */
213#define AF_FLAG_CONIC ( 1U << 0 )
214#define AF_FLAG_CUBIC ( 1U << 1 )
215#define AF_FLAG_CONTROL ( AF_FLAG_CONIC | AF_FLAG_CUBIC )
216
217 /* point touch flags */
218#define AF_FLAG_TOUCH_X ( 1U << 2 )
219#define AF_FLAG_TOUCH_Y ( 1U << 3 )
220
221 /* candidates for weak interpolation have this flag set */
222#define AF_FLAG_WEAK_INTERPOLATION ( 1U << 4 )
223
224 /* the distance to the next point is very small */
225#define AF_FLAG_NEAR ( 1U << 5 )
226
227
228 /* edge hint flags */
229#define AF_EDGE_NORMAL 0
230#define AF_EDGE_ROUND ( 1U << 0 )
231#define AF_EDGE_SERIF ( 1U << 1 )
232#define AF_EDGE_DONE ( 1U << 2 )
233#define AF_EDGE_NEUTRAL ( 1U << 3 ) /* edge aligns to a neutral blue zone */
234
235
236 typedef struct AF_PointRec_* AF_Point;
237 typedef struct AF_SegmentRec_* AF_Segment;
238 typedef struct AF_EdgeRec_* AF_Edge;
239
240
241 typedef struct AF_PointRec_
242 {
243 FT_UShort flags; /* point flags used by hinter */
244 FT_Char in_dir; /* direction of inwards vector */
245 FT_Char out_dir; /* direction of outwards vector */
246
247 FT_Pos ox, oy; /* original, scaled position */
248 FT_Short fx, fy; /* original, unscaled position (in font units) */
249 FT_Pos x, y; /* current position */
250 FT_Pos u, v; /* current (x,y) or (y,x) depending on context */
251
252 AF_Point next; /* next point in contour */
253 AF_Point prev; /* previous point in contour */
254
255 } AF_PointRec;
256
257
258 typedef struct AF_SegmentRec_
259 {
260 FT_Byte flags; /* edge/segment flags for this segment */
261 FT_Char dir; /* segment direction */
262 FT_Short pos; /* position of segment */
263 FT_Short delta; /* deviation from segment position */
264 FT_Short min_coord; /* minimum coordinate of segment */
265 FT_Short max_coord; /* maximum coordinate of segment */
266 FT_Short height; /* the hinted segment height */
267
268 AF_Edge edge; /* the segment's parent edge */
269 AF_Segment edge_next; /* link to next segment in parent edge */
270
271 AF_Segment link; /* (stem) link segment */
272 AF_Segment serif; /* primary segment for serifs */
273 FT_Pos score; /* used during stem matching */
274 FT_Pos len; /* used during stem matching */
275
276 AF_Point first; /* first point in edge segment */
277 AF_Point last; /* last point in edge segment */
278
279 } AF_SegmentRec;
280
281
282 typedef struct AF_EdgeRec_
283 {
284 FT_Short fpos; /* original, unscaled position (in font units) */
285 FT_Pos opos; /* original, scaled position */
286 FT_Pos pos; /* current position */
287
288 FT_Byte flags; /* edge flags */
289 FT_Char dir; /* edge direction */
290 FT_Fixed scale; /* used to speed up interpolation between edges */
291
292 AF_Width blue_edge; /* non-NULL if this is a blue edge */
293 AF_Edge link; /* link edge */
294 AF_Edge serif; /* primary edge for serifs */
295 FT_Int score; /* used during stem matching */
296
297 AF_Segment first; /* first segment in edge */
298 AF_Segment last; /* last segment in edge */
299
300 } AF_EdgeRec;
301
302#define AF_SEGMENTS_EMBEDDED 18 /* number of embedded segments */
303#define AF_EDGES_EMBEDDED 12 /* number of embedded edges */
304
305 typedef struct AF_AxisHintsRec_
306 {
307 FT_Int num_segments; /* number of used segments */
308 FT_Int max_segments; /* number of allocated segments */
309 AF_Segment segments; /* segments array */
310#ifdef AF_SORT_SEGMENTS
311 FT_Int mid_segments;
312#endif
313
314 FT_Int num_edges; /* number of used edges */
315 FT_Int max_edges; /* number of allocated edges */
316 AF_Edge edges; /* edges array */
317
318 AF_Direction major_dir; /* either vertical or horizontal */
319
320 /* two arrays to avoid allocation penalty */
321 struct
322 {
323 AF_SegmentRec segments[AF_SEGMENTS_EMBEDDED];
324 AF_EdgeRec edges[AF_EDGES_EMBEDDED];
325 } embedded;
326
327
328 } AF_AxisHintsRec, *AF_AxisHints;
329
330
331#define AF_POINTS_EMBEDDED 96 /* number of embedded points */
332#define AF_CONTOURS_EMBEDDED 8 /* number of embedded contours */
333
334 typedef struct AF_GlyphHintsRec_
335 {
336 FT_Memory memory;
337
338 FT_Fixed x_scale;
339 FT_Pos x_delta;
340
341 FT_Fixed y_scale;
342 FT_Pos y_delta;
343
344 FT_Int max_points; /* number of allocated points */
345 FT_Int num_points; /* number of used points */
346 AF_Point points; /* points array */
347
348 FT_Int max_contours; /* number of allocated contours */
349 FT_Int num_contours; /* number of used contours */
350 AF_Point* contours; /* contours array */
351
352 AF_AxisHintsRec axis[AF_DIMENSION_MAX];
353
354 FT_UInt32 scaler_flags; /* copy of scaler flags */
355 FT_UInt32 other_flags; /* free for style-specific */
356 /* implementations */
357 AF_StyleMetrics metrics;
358
359 FT_Pos xmin_delta; /* used for warping */
360 FT_Pos xmax_delta;
361
362 /* Two arrays to avoid allocation penalty. */
363 /* The `embedded' structure must be the last element! */
364 struct
365 {
366 AF_Point contours[AF_CONTOURS_EMBEDDED];
367 AF_PointRec points[AF_POINTS_EMBEDDED];
368 } embedded;
369
370 } AF_GlyphHintsRec;
371
372
373#define AF_HINTS_TEST_SCALER( h, f ) ( (h)->scaler_flags & (f) )
374#define AF_HINTS_TEST_OTHER( h, f ) ( (h)->other_flags & (f) )
375
376
377#ifdef FT_DEBUG_AUTOFIT
378
379#define AF_HINTS_DO_HORIZONTAL( h ) \
380 ( !_af_debug_disable_horz_hints && \
381 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_HORIZONTAL ) )
382
383#define AF_HINTS_DO_VERTICAL( h ) \
384 ( !_af_debug_disable_vert_hints && \
385 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_VERTICAL ) )
386
387#define AF_HINTS_DO_BLUES( h ) ( !_af_debug_disable_blue_hints )
388
389#else /* !FT_DEBUG_AUTOFIT */
390
391#define AF_HINTS_DO_HORIZONTAL( h ) \
392 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_HORIZONTAL )
393
394#define AF_HINTS_DO_VERTICAL( h ) \
395 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_VERTICAL )
396
397#define AF_HINTS_DO_BLUES( h ) 1
398
399#endif /* !FT_DEBUG_AUTOFIT */
400
401
402#define AF_HINTS_DO_ADVANCE( h ) \
403 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_ADVANCE )
404
405#define AF_HINTS_DO_WARP( h ) \
406 !AF_HINTS_TEST_SCALER( h, AF_SCALER_FLAG_NO_WARPER )
407
408
409
410 FT_LOCAL( AF_Direction )
411 af_direction_compute( FT_Pos dx,
412 FT_Pos dy );
413
414
415 FT_LOCAL( FT_Error )
416 af_axis_hints_new_segment( AF_AxisHints axis,
417 FT_Memory memory,
418 AF_Segment *asegment );
419
420 FT_LOCAL( FT_Error)
421 af_axis_hints_new_edge( AF_AxisHints axis,
422 FT_Int fpos,
423 AF_Direction dir,
424 FT_Bool top_to_bottom_hinting,
425 FT_Memory memory,
426 AF_Edge *edge );
427
428 FT_LOCAL( void )
429 af_glyph_hints_init( AF_GlyphHints hints,
430 FT_Memory memory );
431
432 FT_LOCAL( void )
433 af_glyph_hints_rescale( AF_GlyphHints hints,
434 AF_StyleMetrics metrics );
435
436 FT_LOCAL( FT_Error )
437 af_glyph_hints_reload( AF_GlyphHints hints,
438 FT_Outline* outline );
439
440 FT_LOCAL( void )
441 af_glyph_hints_save( AF_GlyphHints hints,
442 FT_Outline* outline );
443
444 FT_LOCAL( void )
445 af_glyph_hints_align_edge_points( AF_GlyphHints hints,
446 AF_Dimension dim );
447
448 FT_LOCAL( void )
449 af_glyph_hints_align_strong_points( AF_GlyphHints hints,
450 AF_Dimension dim );
451
452 FT_LOCAL( void )
453 af_glyph_hints_align_weak_points( AF_GlyphHints hints,
454 AF_Dimension dim );
455
456#ifdef AF_CONFIG_OPTION_USE_WARPER
457 FT_LOCAL( void )
458 af_glyph_hints_scale_dim( AF_GlyphHints hints,
459 AF_Dimension dim,
460 FT_Fixed scale,
461 FT_Pos delta );
462#endif
463
464 FT_LOCAL( void )
465 af_glyph_hints_done( AF_GlyphHints hints );
466
467/* */
468
469#define AF_SEGMENT_LEN( seg ) ( (seg)->max_coord - (seg)->min_coord )
470
471#define AF_SEGMENT_DIST( seg1, seg2 ) ( ( (seg1)->pos > (seg2)->pos ) \
472 ? (seg1)->pos - (seg2)->pos \
473 : (seg2)->pos - (seg1)->pos )
474
475
476FT_END_HEADER
477
478#endif /* AFHINTS_H_ */
479
480
481/* END */
482